This invention relates generally to gas turbine engines, and, more particularly, to control of air pressure within a bearing oil sump during all operating conditions.
A gas turbine engine typically includes at least one bearing assembly that supports a rotatable shaft. Each bearing assembly is housed within a sump to which lubricating oil is supplied from a supply pump and from which lubricating oil is scavenged and passed through an oil/air separator and a heat exchange system for cleaning and cooling before being returned to the lubricating oil supply system. To control oil leakage from the sump, some gas turbine engines employ bearing sumps housed within pressurized cavities sealed with circumferential labyrinth seals and supplied with air under pressure to minimize oil leakage. Certain aero-derivative gas turbine engines, such as the LMS100, sold by the assignee of this case, require vent sump pressure control to prevent escape of lubricating oil from an oil sump and to prevent oil consumption when operating at high power and corresponding high inlet pressure.
In some prior art gas turbine engines, as shown, for example, in U.S. Pat. No. 6,470,666 B1, issued Oct. 29, 2002 to Przytulski et al. and assigned to the assignee of the present case, a sump evacuation system is employed to lower air pressure inside a sump pressurization cavity to prevent oil leakage during low power or idle operation. As the power levels of gas turbines has been raised, a system to control oil leakage at high power is needed.